Deflectable Mapping Guide Sheath for His Bundle Pacing

ABSTRACT

A delivery device for delivering a pacing lead to the His bundle of a patient&#39;s heart includes an elongated sheath having a distal end, and a plurality of mapping electrodes positioned at the distal end. The distal end of the sheath may have a distal tip, and the mapping electrodes may include two electrodes that diametrically oppose one another at a position spaced from the distal tip of the sheath. The sheath includes a plurality of flexible sections spaced apart from one another, and a pull wire that causes the sheath to deflect from a straight configuration to a dual hinged curved configuration that positions the electrodes in the vicinity of the bundle of His.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims the benefit of the filing dates of U.S.Provisional Patent Application Nos. 62/710,431, filed on Feb. 16, 2018,and 62/743,460, filed on Oct. 9, 2018, the disclosures of which arehereby incorporated by reference herein.

FIELD OF THE INVENTION

The present disclosure relates to cardiac resynchronization therapy(CRT), and more particularly to pacing of the His bundle in the heart ofa patient. Still more particularly, the present invention relates to amapping guide sheath for locating the His bundle and guiding anelectrode lead thereto.

BACKGROUND OF THE INVENTION

Cardiac rhythm management systems are useful for electricallystimulating a patient's heart to treat various cardiac arrhythmias. Thecurrent standard of care is to pace the right ventricle by myocardialstimulation. In this technique, pacemaker leads are placed at the apexof the right ventricle and at the AV node, the coronary sinus or theleft ventricle, and a pacemaker sends electrical pulses to these areasof the heart. While effective, this technique can cause abnormalelectrical activation sequences resulting in mechanical ventriculardyssynchrony and an increased risk of heart failure, atrial fibrillationand overall mortality.

An alternative approach has been proposed in which an electrode lead isplaced into the bundle of His located either in the septal wall of theright atrium or subvalvular from the right ventricle also in the atrialseptum. As part of the electrical conduction system of the heart, thebundle of His transmits electrical impulses from the atrioventricular(AV) node to the ventricles of the heart. As the electrical impulsesthat regulate the heartbeat are conducted through the bundle of His fromthe right atrium to the left and right ventricles, a lead placed in orin close proximity to the bundle of His would enable the entireelectrical conduction system to be paced in a physiologically naturalway. Pacing the ventricles in this manner, which closely mimics normalAV conduction, can greatly reduce or eliminate the risks associated withtraditional CRT pacing.

While the improved results obtainable with His pacing have beenrecognized, in practice His pacing is difficult to achieve because thebundle of His is very small and difficult to locate and access withavailable devices. The bundle of His has a nominal length of about 5 mmand a nominal width of about 2 mm. It generates an electrical signalthat is a small fraction of that generated by the ventricles. As aresult of its small size and weak electrical signal, the bundle of Hisis extremely difficult to find with a conventional pacing lead.Moreover, once the bundle of His has been located, it is difficult tomaintain the position of the lead while it is being affixed to thecardiac tissue. The difficulties involved in locating the bundle of Hisand affixing a pacing lead thereto are reflected in the time it takes toimplant the leads of an electrical stimulation device, such as apacemaker. In a typical case, implanting biventricular leads can becompleted in as little as 1 minute. To the contrary, the placement of asingle lead for His pacing may take 30 minutes or more, frequentlywithout success. In those cases, the physicians typically revert toconventional lead placement.

There therefore is a need for improvements to the devices used todeliver and implant electrode leads to make it easier to locate thebundle of His and to accurately implant an electrode therein.

BRIEF SUMMARY OF THE INVENTION

One aspect of the present invention provides a delivery device fordelivering a pacing lead to the His bundle of a patient's heart. Thedelivery device includes a handle; an elongated sheath having a proximalend connected to the handle and a distal end remote from the handle, adistal portion of the sheath having a plurality of flexible sectionsspaced from one another along a length of the sheath; a pull wire havinga distal end connected to the sheath distal to the flexible sections andextending to a proximal end; and a plurality of mapping electrodespositioned on the distal end of the sheath.

Another aspect of the present invention provides a method for deliveringa pacing lead to the His bundle of a patient's heart. The methodincludes providing a delivery device having a sheath with an axial lumenand a distal end face; inserting the sheath into the patient's bodythrough the superior vena cava until a distal end portion of the sheathis positioned in the right atrium of the patient; inserting a pacinglead into the axial lumen of the sheath; deflecting the distal endportion of the sheath so that the distal end face of the sheathconfronts the wall of the right atrium; and moving the distal end faceof the sheath relative to the wall of the right atrium until electrodeson the distal end face of the sheath receive electrical signals from thebundle of His.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments of the present guide sheath and methods for usingsame are disclosed herein with reference to the drawings, wherein

FIG. 1 is a highly schematic cutaway view of the heart illustrating animplantable cardiac pacing system;

FIG. 2 is a highly schematic cutaway view of the heart showing theposition of the His bundle relative to other cardiac structures;

FIG. 3 is a diagrammatic view showing the use of a prior art deliverydevice to locate and implant a pacing lead near the bundle of His;

FIG. 4 is a side view of a pacing lead delivery device according to thepresent disclosure;

FIG. 5A is a perspective view showing the layers of the delivery devicesheath and the components used in assembling the sheath;

FIG. 5B is a longitudinal cross-section of the delivery device sheath;

FIG. 5C is a transverse cross-section taken along line 5C-5C of FIG. 5B;

FIG. 6 is an enlarged view of the distal end of the delivery devicesheath;

FIG. 7A is an enlarged side view of the distal tip of the deliverydevice sheath showing the positions of the mapping electrodes thereon;

FIG. 7B is an enlarged view of a portion of FIG. 7A;

FIG. 7C is a highly schematic enlarged longitudinal cross-section of theillustration shown in FIG. 7B;

FIG. 7D is an enlarged view of the distal end of the delivery devicesheath in a deflected condition;

FIG. 8 is a perspective view of one embodiment of a sheath electrode;

FIG. 9 is a perspective view of another embodiment of a sheathelectrode;

FIG. 10 is a perspective view of yet another embodiment of a sheathelectrode;

FIG. 11 is a perspective view of still a further embodiment of a sheathelectrode;

FIGS. 12A-D are highly schematic longitudinal cross-sections of thesheath electrode of FIG. 10 embedded in a sheath;

FIG. 13 is an exploded view showing a method of assembling the sheathelectrode of FIG. 10 to a sheath;

FIG. 14 is a longitudinal cross-section through the handle of thedelivery device shown in FIG. 4;

FIG. 15 is a perspective view of the distal end of the delivery devicehandle showing the slitting channel;

FIG. 16 is an enlarged view of the distal end of the delivery devicesheath in a deflected condition;

FIG. 17 is a diagrammatic view showing certain distances relative tostructures in the heart;

FIG. 18 is a highly schematic side view of a pacing lead;

FIGS. 19A-D illustrate a process by which the delivery device of FIG. 4locates the bundle of His and implants a pacing lead therein;

FIG. 20 is a diagrammatic view showing the use of the delivery device ofFIG. 4 to locate and implant a pacing lead in the bundle of His;

FIG. 21 is a partial view showing a sheath slitter attached to thedistal housing portion of the delivery device handle;

FIG. 22A is a longitudinal cross-section through the distal housingportion of the delivery device handle shown in FIG. 14; and

FIG. 22B is a longitudinal cross-section through the distal housingportion of a delivery device handle according to another embodiment ofthe disclosure.

DETAILED DESCRIPTION

As used herein, the terms “proximal” and “distal,” when used inreference to a delivery device, are to be taken as relative to a user ofthe delivery device. “Proximal” is to be understood as relatively closeto the user and “distal” is to be understood as relatively far away fromthe user. As used herein, the terms “substantially,” “generally,” and“about” are intended to mean that slight deviations from absolute areincluded within the scope of the term so modified.

FIG. 1 is a highly schematic cutaway view of heart 10 illustrating theright atrium RA, the right ventricle RV, the left atrium LA, and theleft ventricle LV. During normal operation of heart 10, deoxygenatedblood from the body is returned to the right atrium RA from the superiorvena cava 12 and inferior vena cava 14. The right atrium pumps the bloodthrough the atrioventricular or tricuspid valve 16 to the rightventricle RV, which then pumps the blood through the pulmonary valve 18and the pulmonary artery 20 to the lungs for reoxygenation and removalof carbon dioxide. The newly oxygenated blood from the lungs istransported to the left atrium LA, which pumps the blood through themitral valve 22 to the left ventricle LV. The left ventricle LV pumpsthe blood through the aortic valve 24 and the aorta 26 throughout thebody.

FIG. 2 is another schematic cutaway view showing the location of thebundle of His 30 in the heart. The bundle consists of fast-conductingmuscle fibers that begin at the atrioventricular node in the rightatrium and pass to the interventricular septum. The bundle divides inthe septum into a right branch that travels along the right side of theseptum and supplies excitation to the right ventricle, and a pair ofleft branches that travel along the left side of the septum and supplyexcitation to the left ventricle. The fibers in the branches terminatein an extensive network of Purkinje fibers which distribute excitationpulses to the layer of cells beneath the endocardium.

Returning to FIG. 1, also shown is a schematic view of a prior art Hisbundle mapping and pacing system 50. System 50 includes a subcutaneouslydisposed stimulation device or pacemaker 52 coupled to a pulsing lead 54designed to penetrate the endocardium in contact with His bundle 30.Lead 54 enters the vascular system through one of several possiblevascular access sites and extends through the superior vena cava 12 tothe right atrium RA.

FIG. 3 is a diagrammatic view showing the use of lead 54 to locate thebundle of His 30. While it is being maneuvered through the patient'svasculature to the right atrium RA, lead 54 is held within a protectivesheath 56. In a conventional system, sheath 56 may have a fixed curvethat approximates the position of the bundle of His relative to thesuperior vena cava 12. Once sheath 56 is in the right atrium, the tip oflead 54 is advanced out from the sheath to expose electrodes 60 and 62and helical fixation anchor 64. Electrodes 60 and 62 may be spaced aparton lead 54 by up to about 10 mm. Sheath 56 may be manipulated to advancelead 54 parallel to the atrial wall until the faint electrical signalsfrom His bundle 30 are identified. This typically occurs when electrodes60 and 62 are on opposite sides of the bundle, as depicted in FIG. 3. Atthis point, sheath 56 may be manipulated to implant fixation anchor 64in the atrial wall. However, as fixation anchor 64 is distal toelectrodes 60 and 62, when the electrodes detect the bundle of His 30,the fixation anchor is at a position spaced several millimeters from thebundle. Hence, if implanted at this location, fixation anchor 64 andlead electrodes 60 and 62 will be offset from the bundle of His, suchthat any pacing pulses from pacemaker 52 may not stimulate and pace theHis bundle.

The present disclosure is directed to a delivery device configured toaddress the foregoing difficulty in locating and implanting leadelectrodes in the bundle of His 30. One embodiment of a delivery device100 according to the present disclosure is shown in FIG. 4. Deliverydevice 100 includes four major components or assemblies, including asheath 102, a handle 202, a connector assembly 302, and a hub 402 (FIG.14). Connector assembly 302 typically includes electrodes mounted on theouter surface of sheath 102 near its distal end and a connector disposednear handle 202. Conductive wires electrically connect the electrodes tothe connector. Connector assembly 302 is electrically linked to anexternal electrogram mapping system. Handle 202 is connected to theproximal end of sheath 102 and includes a mechanism for deflecting thedistal end of the sheath. Hub 402 is positioned in handle 202 and has acentral opening that accepts the proximal end of sheath 102 and throughwhich a pacing lead is introduced and advanced into the sheath. Each ofsheath 102, handle 202, connector assembly 302, and hub 402 is describedin more detail below.

Sheath 102 has a structure and configuration that reliably introduces apacing lead into a patient's heart, while exhibiting a high degree ofmaneuverability as well as the ability for its distal end portion to bedeflected. It is therefore desirable that sheath 102 have a sufficientdegree of columnar strength for advancement through the tortuousvasculature of the patient, and sufficient kink resistance to bendsmoothly. Sheath 102 achieves these characteristics from a multi-layerconstruction as shown in FIGS. 5A-5C. An inner layer 110 of sheath 102may be formed from a tube of a lubricious material to facilitate thepassage of a pacing lead through the sheath, as well as the rotation ofthe lead within the sheath as it is being fixed to heart tissue. Onesuch lubricious material may be polytetrafluoroethylene (PTFE).

PTFE materials exhibit a high degree of chemical inertness andhydrophobicity, and therefore do not readily adhere to other polymers.In order to integrate inner layer 110 with the other layers of sheath102, the outer surface of layer 110 may be chemically activated throughphysical and/or chemical surface treatment methods, including chemicalplasma treatment or chemical etching processes known in the art. In onesuch process, a fluorocarbon etchant containing sodium naphthalene maybe utilized to chemically treat the outer surface of layer 110 through aseries of process steps, including an etching step, several rinsingsteps and a drying step. In the etching step, layer 110 may be immersedin the etchant at a temperature of between about 55° C. and about 65° C.in a tight vessel with nitrogen purging for a duration of between about30 seconds and a few minutes. Light agitation of the etchant may helppromote the etching effect. Following the etching step, the etchant maybe drained from the vessel and layer 110 may be subjected to a series ofsuccessive rinsing steps, each at a temperature of about 70° C. In thefirst rinsing step, layer 110 is immersed in an alcohol bath(containing, for example, between about 75 w t% and about 90 wt %isopropanol or methanol) for between about 5 seconds and about 20seconds. The alcohol chemically deactivates and partially dissolvessodium naphthalene. In the second rinsing step, layer 110 is immersed inchlorine-free carbon-filtered, distilled or deionized water for betweenabout 15 seconds and about 30 seconds. The second rinsing step may befollowed by a third rinsing step in which layer 110 is immersed in anacidic water bath (containing between about 2 wt % and about 5 wt %acidic acid) for about 60 seconds. The pH of the acidic water bathshould be between about 4 and about 6. The acidity of the bathneutralizes the alkalinity of the etchant and produces a faster and morethorough cleaning effect. Following the rinsing steps, layer 110 may bedried, for example using forced hot air or an oven at between about 70°C. and about 80° C. until fully dried. During the chemical etching oflayer 110, the inner lumen thereof should be sealed off or otherwiseprotected so as to maintain its inherent surface lubricity.

Layer 110 may be followed by a braided layer 112 to provide stability tosheath 102. Braided layer 112 may include a plurality of metallic braidsimpregnated with one or more thermoplastic polymers. Examples ofacceptable thermoplastic polymers include polyamides, such as nylon 11,nylon 12, nylon 612, and the like; polyesters, such as polybutyleneterephthalate), poly(ethylene terephthalate), and the like; andthermoplastic elastomers, such as poly(ether-block-amide) copolymerresins, poly(ether-co-ester) block copolymer resins, and variousthermoplastic polyurethane block copolymer resins. To form braided layer112, a first one of the aforementioned thermoplastic polymers may beextruded onto a mandrel whose outer diameter is approximately equal tothe lumen diameter of layer 110 to form an inner jacket layer.Multi-thread metallic wires may then be braided over the inner jacketlayer. The wires may be round, with diameters of from about 0.02 mm toabout 0.2 mm, or flat, with sizes ranging from about 0.01 mm thick byabout 0.05 mm wide to about 0.1 mm thick by about 0.20 mm wide. Thebraid can be woven with a regular, full-load pattern (with one wirepassing under two wires and then over two wires), a diamond pattern(with two side-by-side wires alternately passing under two side-by-sidewires then over two side-by-side wires), a half-load diamond pattern(with one wire passing under one wire and then over one wire) or otherpatterns known in the art.

Following the braiding step, another of the aforementioned thermoplasticpolymers may be extruded over the braids to form an outer jacket layer.The thermoplastic polymers forming the inner and outer jacket layers canbe the same, similar or different. However, they should be chemicallycompatible or miscible so that the polymer of the outer jacket layerstrongly adheres to the polymer of the inner jacket layer as it isextruded thereover. This strong adherance may be achieved by using apolymer with a relatively lower melt temperature for the inner jacketlayer and a polymer with a relatively higher melt temperature for theouter jacket layer. As a result, the polymer of the outer jacket layerwill thermally fuse and strongly adhere to the polymer of the innerjacket layer, embedding the metallic braids therebetween.

Sheath 102 further includes an outer polymer layer 114 disposed overbraided layer 112. Outer layer 114 preferably provides columnar strengthin the proximal and middle sections of sheath 112 and deflectability inthe distal section of the sheath. Layer 114 may be formed from anypolymer capable of being extruded to the desired dimensions and ofproviding the proper stiffness and stability, including any of thethermoplastic polymers described above for forming braided layer 112.One such material is a polyether block amide sold under the name Pebax®by Arkema France. The proximal section 115 and middle section 117 ofouter layer 114 may be formed from a tube of a polymer having a hardnessof about 60 to about 100 on the Shore D scale as measured by adurometer, with a Shore D hardness of about 70 to about 75 beingpreferred. In a distal section of sheath 102, shown more clearly in FIG.6, layer 114 includes two sections 116 and 118 of a less hard, andtherefore more pliable, material. Sections 116 and 118 may also beformed from tubes of Pebax® polyether block amide or anotherthermoplastic elastomer, but with a Shore D hardness of between about 20and about 40, preferably about 35. Sections 116 and 118 each may have alength in the axial direction of sheath 102 of between about 1 cm andabout 3 cm. In a preferred arrangement, each of sections 116 and 118 mayhave a length in the axial direction of sheath 102 of between about 1.5cm and about 2 cm. The distalmost section 116 may be spaced from thedistal end 120 of sheath 102 by between about 1 cm and about 3 cm,preferably by between about 1.5 cm and about 2.5 cm. The proximalmostsection 118 may be spaced from section 116 by between about 0.5 cm andabout 2 cm, preferably by between about 1 cm and about 2 cm. The section122 of outer layer 114 between sections 116 and 118, and the section 124of layer 114 between distal end 120 and section 116 are preferably madefrom the same relatively rigid material as the proximal section 115 andmiddle section 117 of the outer layer. Sections 116 and 118 may bejoined to the other sections of layer 114 by gluing, ultrasonic welding,reflow heating or other known techniques. In a preferred arrangement,the distal tip of sheath 102 may be formed from Pebax® or anotherpolymer that is softer than the material forming section 124 so as toprovide an atraumatic tip to the sheath. In some embodiments, thepolymers forming layer 114 may include radiopaque fillers, such asbarium sulfate, tungsten, bismuth trioxide, bismuth subcarbonate,bismuth oxychloride and the like. Polymers containing a radiopaquefiller may be used for outer layer 114 in different sections of sheath102. A lumen 126 extends continuously through sheath 102 from distal end120 to handle 202. Lumen 126 has a diameter that is slightly larger thanthe diameter of the pacing lead to be delivered to the heart by deliverydevice 100. For example, for a 7 French pacing lead (having a diameterof about 2.33 mm), lumen 126 may have a size of about 7.5 French (adiameter of about 2.5 mm).

A pull wire 130 may extend through a narrow tube 132 extending along thelength of sheath 102 between braided layer 112 and outer layer 114. Inan alternate arrangement, tube 132 may be positioned between inner layer110 and braided layer 112. Tube 132 is preferably formed from a materialthat will resist collapsing or kinking during the manufacture of sheath102 and the use of delivery device 100. Materials appropriate forforming tube 132 include polyetherimide, polyimide, PTFE or other hightemperature polymers. Optionally, tube 132 may include metal braids tofurther enhance its kink resistance. Pull wire 130 may be affixed at itsdistal end to a pull wire ring 134 and at its proximal end to anoperating mechanism in handle 202, described more fully below. Pull wirering 134 is located distally of sheath section 116 near the distal end120 of the sheath, and is fixed in place between braided layer 112 andouter layer 114.

Near its distal end 120, sheath 102 includes a pair of split ringmapping electrodes 310 and 312, as shown in FIGS. 5B and 7A. Electrodes310 and 312 are part of connector assembly 302, and they may beidentical to one another. Any appropriate metal, such asplatinum-iridium, may be used to form electrodes 310 and 312, and theymay be diametrically opposed to one another on opposite sides of sheath102. For a sheath having a conventional size, the ends of electrode 310may be spaced apart in the circumferential direction from the ends ofelectrode 312 by between about 1 mm and about 3 mm, preferably by about2.5 mm. An electrical conductor 314 may extend from each of electrodes310 and 312 through a narrow tube 140 extending along the length ofsheath 102 between braided layer 112 and outer layer 114 or betweeninner layer 110 and braided layer 112. Tube 140 may be formed from thesame polymer used to form tube 132, and may optionally include metalbraids to enhance its kink resistance. Upon exiting tube 140, conductors314 may travel through a lumen (not shown) in handle 202 and through aconduit 320 to an electrical connector 340.

To fabricate sheath 102, its individual components may be sequentiallyassembled over a supporting core rod 500. Thus, after treatment of itsouter surface, inner layer 110 may be assembled over core rod 500,followed by braided layer 112. Pull wire ring 134 may then be positionedover braided layer 112 near the distal end of sheath 102, and tubes 132and 140 may be positioned alongside the braided layer. Alternatively,tubes 132 and 140 may be positioned against inner tube 110 and braidedlayer 112 may be assembled thereover. Pull wire 130 may be threaded frompull wire ring 134 through tube 132 and out from the proximal endthereof. Similarly, electrical conductors 314 may be threaded throughtube 140 and out from the proximal end thereof. As will be appreciatedfrom the discussion below, tube 132 and pull wire 130 preferably arepositioned along the side of braided layer 112 toward which sheath 102is to be deflected. Tube 140 and electrical conductors 314 may bepositioned on the side of braided layer 112 diametrically opposed totube 132 or at another position around the circumference of the braidedlayer. Sections 115, 117 (which together may comprise a single tube),116, 118, 120 and 122 of outer layer 114 may then be assembled over thepreviously assembled components. When all of the individual componentsof sheath 102 have been assembled together and their relative positionshave been properly adjusted, a heat-shrinkable tube 510 may be appliedto fully encapsulate the assembly. When heated in a reflow process to anappropriate thermal lamination temperature near or above the criticalthermal transition temperatures of the polymers used for braided layer112 and outer polymer layer 114, those layers will partially orcompletely melt, thermally bonding the layers to one another and toinner layer 110. Although the inner layer 110 will not melt, thechemical etching of its surface will cause the polymers of braided layer112 to strongly adhere to it.

Although braided layer 112 was described above as including metal braidsembedded in inner and outer polymer jacket layers, that may not be thecase. In an alternate embodiment, braided layer 112 can be formed simplyby forming the metal braids on a disposable mandrel without the polymerjacket layers. In such arrangement, the individual components of sheath102 would be assembled as described above, with the metal braided layer112 assembled over inner layer 110 (and over or under tubes 132 and140), and, with pull wire 130, pull wire ring 134, and conductors 314properly positioned, the sections of outer layer 114 may be assembledthereover. During the subsequent reflow process, the polymers of outerlayer 114 will melt, permeate the metal braids and fuse to inner layer110.

As electrodes 310 and 312 are split ring electrodes that do not fullycircumscribe sheath 102, the electrodes must be strongly attached to thesheath so as to not become detached therefrom upon advancement of thesheath through the patient's vasculature to deliver a pacing lead to thebundle of His 30 or during removal of the sheath from the patientfollowing such procedure. Thus, while electrodes 310 and 312 may bepositioned at the tip of sheath 102 to thereby be exposed on the distalend face of the sheath, the electrodes are preferably spaced from thetip of the sheath so as to be surrounded on all sides by a continuousmass of the sheath polymer.

FIGS. 7A-C illustrate the positions of electrodes 310 and 312 at thedistal end 120 of sheath 102. The positions of electrodes 310 and 312 onsheath 102 are based generally on two considerations obtaining thestrongest signal from the bundle of His, and assuring the adherance ofthe electrodes to the sheath. As noted, it is preferably to spaceelectrodes 310 and 312 from the tip of sheath 102 to more securelyadhere the electrodes to the sheath. However, the ability of theelectrodes to sense signals from the bundle of His is greatest when theelectrodes are exposed on the distal end face of the sheath. As acompromise, it is preferable to position the electrodes as close aspossible to the distal end face of sheath 102 while still allowing aregion 150 of polymer between the electrodes and the tip of the sheath.In one embodiment, recessing the electrodes about 0.5 mm from the tip ofsheath 102 is preferred. In addition to more securely fixing theelectrodes to sheath 102, spacing the electrodes proximally of thedistal tip of the sheath keeps sharp edges of the electrodes from beingexposed, thereby reducing trauma to tissue as delivery device 100 isadvanced through the patient's vasculature. As shown in FIG. 7B, the tipof sheath 102 also may be chamfered, as at 152, further reducing traumaduring the advancement of delivery device 100. Making the distal end ofsheath 102 black or another dark color, as shown in FIG. 7D, willhighlight metallic electrodes 310 and 312 and make them more visible.

Another consideration in where to position electrodes 310 and 312 onsheath 102 has to do with the direction in which the distal tip of thesheath deflects. In that regard, it is preferable to position theelectrodes on sheath 102 so that, when the sheath is deflected, theelectrodes are generally aligned in the direction in which the fibers ofthe bundle of His are oriented. The maximum signal will be detected fromthe bundle of His when both electrode 310 and electrode 312 are locateddirectly thereover. Thus, if electrodes 310 and 312 are oriented onsheath 102 on opposite sides of the deflection plane defined by thedeflected distal tip of the sheath (i.e., at positions located 90° fromthe positions shown in FIG. 7D), only one electrode at a time will beable to be located over the His bundle 30. As sheath 102 is movedrelative to the atrial septal wall in an area in close proximity to theHis bundle, one electrode may move closer to the His bundle while theother electrode may move away from the His bundle, such that the maximumpossible signal will not be obtained. On the other hand, by positioningboth of electrodes 310 and 312 in the deflection plane, as shown in FIG.7D, both electrodes can lie over the bundle of His 30 at the same time.In fact, as sheath 102 is moved across the atrial septal wall, therewill be a distance equal to about the diameter of the sheath withinwhich the maximum His bundle signal can be detected.

In order to assemble electrodes 310 and 312 to sheath 102, a portion ofthe polymer is first removed from areas on opposite sides of the distalend of the sheath, creating cavities 154 and 156 sized to receive theelectrodes. Cavities 154 and 156 may be formed either before or afterassembling the components of sheath 102. In one example, the polymer maybe removed by laser ablation, although other removal techniques known inthe art may also be employed, including but not limited to cutting,grinding, chemical etching and the like. Preferably, the polymer isremoved to a depth that is substantially the same as the radialthickness of electrodes 310 and 312 so that, once assembled to sheath102, the outer surface of the electrodes will be substantially flushwith the outer surface of the sheath. After conductor 314 has beenassembled to each of electrodes 310 and 312, the electrodes are insertedinto cavities 154 and 156, respectively, and the distal end of thesheath may again be subjected to a reflow heating process to partiallyor completely melt the outer polymer of braided layer 112 and outerpolymer layer 114 to mechanically bond the electrodes to the sheath.FIG. 7C is a cross-sectional view showing electrode 310 embedded withinthe polymer at the distal end of sheath 102.

FIGS. 8-13 illustrate examples of structures for forming electrodes 310and 312 to facilitate their secure assembly to sheath 102. Each of thecurved structures shown in these figures may be laser cut or otherwiseformed from a metal tube having a circumference that is substantiallysimilar to the circumference of sheath 102 so that the curvature of theresultant electrodes matches that of the sheath. Structures not shownwith a curved configuration may be formed flat from flat sheet stock andsubsequently bent to have a curvature that matches the curvature ofsheath 102.

The electrode 800 shown in FIG. 8 is generally in the form of a plate802 having a curvature that is substantially similar to the curvature ofthe outer surface of sheath 102. The side edges 804 a and 804 b of plate802 (i.e., the edges that are substantially parallel to the longitudinalaxis of sheath 102) are beveled so that, during the reflow heatingprocess, the softened or molten polymer can flow over the beveled edgesto securely hold electrode 800 to the sheath. Rather than the side edgesof plate 802 being beveled, electrode 800 may be formed so that the endedges 806 a and 806 b of plate 802 (i.e., the edges that aresubstantially orthogonal to the longitudinal axis of sheath 102) may bebeveled, or both the side edges and end edges may be beveled. Plate 802may optionally include an aperture 808 that may fill with polymer duringthe reflow heating process to further prevent electrode 800 from movinglongitudinally relative to the sheath.

In the embodiment shown in FIG. 9, a generally flat metal plate 902 maybe formed with a reduced thickness along its side edges 904 a and 904 band end edges 906 a and 906 b. This reduced thickness may be formed by astamping operation, by grinding, machining or other mechanicaltechnique, by chemical etching or by other known techniques. As aresult, the thickness of the side and end edges of plate 902 may be lessthan the thickness of a center region 908. Once the edges of plate 902have been thinned, the plate may be deformed into an electrode 900having a curved shape that substantially matches the curvature of sheath102. Following the attachment of conductor 314, an electrode 900 may beassembled in each of cavities 154 and 156 and the distal end of sheath102 may be subjected to a reflow heating process. During such process,the softened or molten polymer will flow to cover the thinned edges ofelectrodes 900 to firmly hold same in place.

FIG. 10 shows an electrode 1000 that is generally in the form of arectangular plate 1002 having a curvature that is substantially similarto the curvature of the outer surface of sheath 102. The end portions1004 and 1006 of plate 1002 are bent toward one another against theinner surface of plate 1002 as in a conventional staple so that a slightgap 1008 is formed between end portions 1004 and 1006 and the main body1010 of the plate. Following the attachment of conductors 314,electrodes 1000 may be assembled in appropriate positions near thedistal end of sheath 102 and the sheath may be subjected to a reflowheating process. As the polymer of sheath 102 softens, electrodes 1000may sink into the polymer, and the polymer may flow into the gaps 1008between end portions 1004 and 1006 and main body 1010, securely affixingthe electrode to the sheath. Thus, preforming cavities 154 and 156 insheath 102 may not be necessary in this embodiment. While FIG. 10 showsend portions 1004 and 1006 bent at right angles to the sides of plate1002, that need not be the case. End portions 1004 and 1006 may be bentat an angle other than right angles if it is desired to produce anon-rectangular electrode surface.

FIG. 11 shows an electrode 1100 which is a variant of electrode 1000shown in FIG. 10. The difference between the electrodes is that, inaddition to main body 1108 and end portions 1104 and 1106, the plate1102 of electrode 1100 includes projections 1110 and 1112 that protrudefrom the lateral sides of the main body. In addition to folding the endportions 1104 and 1106 of plate 1102 against the inner surface of theplate, projections 1110 and 1112 may be folded inwardly until they coverthe side edges of the end portions. Relative to electrode 1000,electrode 1100 eliminates exposed sharp edges that could damage tissue,and provides a more secure affixation of the electrode to sheath 102,particularly in the circumferential direction.

Different configurations for securing the electrode 1000 of FIG. 10 tosheath 102 are shown in the longitudinal cross-sectional views shown inFIGS. 12A-D. In each configuration, following the attachment of aconductor 314 to each electrode 1000, one electrode is placed into eachof cavities 154 and 156 and the distal end of sheath 102 is subjected toa reflow heating process, locking the electrodes in place. Referring toFIG. 12A, rather than bending the end portions 1004 and 1006 of plate1002 toward one another, end portion 1006 is bent toward the innersurface of plate 1002, while end portion 1004 is bent away from endportion 1006 and main body 1010 so that end portions 1004 and 1006 liein substantially the same plane.

FIG. 12B shows electrode 1000 attached to sheath 102 at a positionspaced from the distal tip of the sheath. Both end portions 1004 and1006 are bent toward one another against the inner surface of plate 1002as described above. FIG. 12C is substantially the same as FIG. 12B.However, rather than being positioned at a spaced distance from thedistal tip of sheath 102, electrode 1000 in FIG. 12C is positioned atthe distal tip of the sheath so that the end of the electrode is exposedon the distal end face of the sheath. As discussed above, assemblingelectrode 1000 to sheath 102 in this position produces the strongestsignal from the bundle of His during a mapping procedure.

The configuration shown in FIG. 12D is similar to the configurationshown in FIG. 12A. However, rather than having one end portion benttoward the main body 1010 of plate 1002, both of end portions 1004 and1006 are bent away from one another and away from main body 1010.Bending one or more of the end portions away from main body 1010, asshown in FIGS. 12A and 12D, facilitates the secure connection ofelectrode 1000 to sheath 102 as it does not require polymer to flow intothe gaps 1008 between the end portions and the main portion 1010 of theelectrode.

Electrode 1000 may also be affixed to sheath 102 in a variant of whathas been described above in connection with FIGS. 10, 11, and 12A-12C.In each of those embodiments, at least one of end portions 1004 and 1006is bent toward the inner surface of plate 1002, creating a gap 1008between the end portion and the main body 1010 of the plate. In thevariant contemplated, a separate strip of Pebax® or other polymer may bepositioned against the inner surface of plate 1002 before the endportions are bent. Thus, after the bending operation, the strip ofPebax® or other polymer will be positioned in and fill gaps 1008.Electrode 1000 may then be assembled to sheath 102 as described above.However, during the reflow process, the sheath polymer will not have tofill gaps 1008, as those gaps will already have been filled. Rather, thepolymer in gaps 1008 will melt and fuse to the other polymer of sheath102, firmly holding electrode 1000 in place.

Another technique for attaching electrode 1000 to sheath 102 is shown inFIG. 13. In this technique, section 116 of outer layer 114 is notassembled to sheath 102 during the sheath assembly process. Rather,slits 160 are formed at appropriate locations in section 116. The endportions 1004 and 1006 of electrode 1000 are then bent to an orientationorthogonal to the main body 1010 of the electrode. Electrode 1000 maythen be assembled to sheath section 116 by inserting end portions 1004and 1006 into slits 160 and bending them against the inner surface ofthe sheath section. End portions 1004 and 1006 may be bent toward oneanother, away from one another, or one end portion may be bent towardthe main body 1010 of plate 1002, while the other end portion is bentaway from the first end portion. With electrode 1000 assembled to sheathsection 116 as described, the sheath section may be assembled over thedistal end of sheath 102, and the distal end of the sheath may again besubjected to a reflow heating process to melt and bond sheath section116 to the underlying braided layer 112, trapping electrode 1000 inplace.

In another variant for attaching any of the electrodes described aboveto sheath 102, the electrode may first be sandwiched between two stripsof Pebax® or other polymer. The strip of polymer on the inner surface ofthe electrode may include an aperture for connecting a conductor 314 tothe electrode. The sandwiched electrode assembly may then be properlypositioned on sheath 102 and subjected to a reflow process through whichthe electrode is strongly affixed to the sheath. Following the reflowprocess, the outer layer of polymer covering the electrode may beremoved by any known technique, including laser ablation, cutting,scraping, grinding and the like to expose the outer surface of theelectrode.

When delivery device 100 is being used to map the location of His bundle30, the free ends of conductors 314 may be connected through connector340 to a patient monitor, electrocardiograph, or other external devicefor displaying the electrical signals detected by electrodes 310 and312. Optionally, sheath 102 may include a ring electrode 350 (FIG. 5B)spaced proximally of mapping electrodes 310 and 312. As ring electrode350 comprises a continuous ring, it may be incorporated in sheath 102during assembly of the sheath, using techniques known in the art.Electrical conductors (not shown) may extend from ring electrode 350 toconnector 340 through tube 140 or through another tube incorporated insheath 102. When available, voltage differences between ring electrode350 and either of split ring electrodes 310 or 312 may be used to mapthe electrical activity of the heart.

Sheath 102 is connected at its proximal end to handle 202. Alongitudinal cross-section of handle 202 is shown in FIG. 14. Handle 202includes a distal housing portion 210 and a proximal housing portion212, both of which are hollow. Housing portions 210 and 212 may bejoined to one another by a rigid alignment rail 214 so as to maintain aspace between the housing portions. Alignment rail 214 may be formedfrom a rigid material, such as glass-filled nylon, and may be connectedto housing portions 210 and 212 by any known fastening mechanism,including screws, press fit connection, ultrasonic welding and the like.Prior to the connection of both ends of alignment rail 214 to thehousing portions, a hollow pull wire screw 220 may be assembled over therail and a rotatable actuator 222 may be assembled over the screw.Actuator 222 has a series of internal threads 224 that mate withexternal threads 226 on screw 220. At one end, actuator 222 has anannular ring 230 that is captured within an annular groove 232 in distalhousing portion 210. At its other end, actuator 222 has a similarannular ring 234 that is captured within an annular groove 236 inproximal housing portion 212. The engagement of ring 230 in groove 232,and the engagement of ring 234 in groove 236, positions actuator 222 inthe space between the housing portions, guides the rotation of theactuator in handle 202, and serves to help maintain the assembly ofdistal housing portion 210 to proximal housing portion 212. As actuator222 is rotated in a first direction, pull wire screw 220 will translateproximally relative to handle 202, and when the actuator is rotated inthe opposite direction, the pull wire screw will translate distallyrelative to the handle. The proximal end of pull wire 130 may be fedthrough pull wire screw 220 for connection in a known manner to theproximal end thereof. Thus, as pull wire screw 220 translatesproximally, it will translate pull wire 130 proximally, and when pullwire screw 220 translates distally, it will translate pull wire 130distally.

Handle 202 also includes a conduit 240 having a connector 242 at itsproximal end for connection to a source of flushing fluid. Conduit 240is connected to a further conduit 244 that travels through handle 202 tohub 402 for supplying the flushing fluid to flush the interior of sheath102. Conduit 320, carrying conductors 314, is connected at one end toconduit 240 by a Y-splitter, and at the other end is connected toelectrical connector 340. Conductors 314 traveling through handle 202exit therefrom through conduits 240 and 320 and are connected bysoldering or the like to pins in electrical connector 340.

Referring to FIG. 14, hub 402 is held in the interior of distal housingportion 210 and fixedly connects the proximal end of sheath 102 tohandle 202. Sheath 102 passes through a hemostasis valve 404 in hub 402,which provides a seal to minimize blood loss from around the sheath. Achannel 250 (FIG. 15) formed in the upper surface of distal housingportion 210 provides access to hub 402 and sheath 102. Channel 250 isadapted to receive a sheath slitter for slitting sheath 102 followingthe insertion of the pacing lead in a patient, as will be explained morefully below.

When pull wire 130 is translated proximally, the pliability of sections116 and 118 enables the distal portion of sheath 102 to deflect from asubstantially straight configuration to the predefined dual hingedconfiguration shown in FIG. 16. By deflecting at these two spacedlocations, sheath 102 assumes a shape that better enables its distal end120 to be positioned to confront the right atrial wall near His bundle30 while the proximal section 115 of the sheath is positioned within thesuperior vena cava 12 of heart 10. Distance X in FIG. 16 is the averagedistance from the central axis of superior vena cava 12, through whichsheath 102 enters the right atrium RA, to tricuspid valve 16, whiledistance Y is the average inner diameter of the tricuspid valve.One-third of distance Y approximates the distance which sheath 102 musttraverse to reach the atrial wall in order to contact or come in closeproximity to His bundle 30. As this distance is an approximation, and asexceeding this distance is not likely to have a negative effect onlocating His bundle 30, it will be appreciated that this distance (whichis approximately the distance from the section 122 of sheath 102 to thedistal end 120 thereof) may be between about ⅓ Y and about ½ Y.Distances X and Y are illustrated relative to the structures of heart 10in the diagrammatic illustration shown in FIG. 17. To complete thedescription, rotating actuator 222 in the opposite direction willtranslate pull wire 130 distally, returning sheath 102 toward thesubstantially straight configuration.

Delivery device 100 may be used to deliver a pacing lead into the rightatrium RA, to map the right atrium to locate His bundle 30, and to fixthe pacing lead therein. One example of such a pacing lead is pacinglead 600 shown schematically in FIG. 18. Lead 600 generally has aflexible elongate body 602 with a proximal end 604, a distal end 606,and a lumen (not shown) extending axially therethrough. A pair ofbipolar electrodes 608, 610 is located at the distal end of body 602.Electrode 610 is positioned at the distal tip of body 602, whileelectrode 608 may be spaced therefrom along the length of the body. Afixation anchor 612 extends distally from the distal end 606 of body 602and forms a part of electrode 610. At the proximal end 604 of body 602,lead 600 includes a pair of electrical contacts 614 and 616. Contacts614 and 616 are each electrically connected to one of electrodes 608 and610 by conductors traveling through the lumen in body 602. Contacts 614and 616 enable pacing lead 600 to be mechanically and electricallyconnected to pacemaker 52, such as by alligator clips or otherconnectors connected to contacts 614 and 616.

The use of delivery device 100 to deliver and fix pacing lead 600 in thebundle of His will now be described with reference to FIGS. 19A-D and20. FIGS. 19A-D illustrate the delivery and fixation of pacing lead 600with respect to an anatomically-accurate transparent model 700 of theright side of the human heart. Model 700 may be used to train operatorsin the His pacing procedure, and to develop and test clinical tools forperforming the procedure. For clarity, the reference numerals used inFIGS. 19A-D to identify the structures of the heart will be the samereference numbers used to identify the structures in the cutaway view ofthe heart illustrated in FIG. 1. The region in which the bundle of Hisis located is simulated in model 700 by a conductive insert (not shown)that may be received in port 710. The insert may be formed of a gel toenable fixation of pacing lead 600 therein, and may have physical and/orelectrical properties that simulate myocardial tissue. The insert mayalso be doped with an ionic material to provide electrical propertiessimilar to those of the His bundle so that electrically-active deliverydevices can be used to map the region. During a mapping and fixationprocedure, the insert may be stimulated electrically by a circuit toproduce an electric signal, preferably one that is similar to thatproduced by the bundle of His. A more detailed description of model 700and its use can be found in commonly owned U.S. patent application Ser.No. 16/208,348, the disclosure of which is hereby incorporated byreference herein.

With electrical conductors 314 electrically connected through connector340 to an external device for receiving signals from electrodes 310 and312, delivery device 100 is inserted through a vascular access site intothe superior vena cava 12, and is maneuvered through the superior venacava to the right atrium RA as illustrated in FIGS. 19A and 19B. Duringthis insertion procedure, the sheath 102 of delivery device 100 may havea substantially straight configuration, and may include a dilator (notshown) positioned in lumen 126 thereof to enlarge the access path and toprovide support to the sheath as it is being maneuvered. The straightconfiguration of sheath 102 facilitates its passage through the superiorvena cava 12 and into the right atrium RA. Once the distal end 120 ofdelivery device 100 has entered the right atrium RA, the dilator may beremoved from the delivery device and pacing lead 600 may be insertedinto lumen 126 in its place. Again, the straight configuration of sheath102 facilitates the insertion of pacing lead 600 therein.

With the distal portion of sheath 102 fully within right atrium RA, theuser may operate delivery device 100 to place sheath 102 in thedeflected configuration shown in FIG. 19C. Since sheath 102 is only ableto deflect in a single direction, the user must first confirm thatdelivery device 100 is in the proper orientation. This may beaccomplished by locating the position of indicia (not shown) at theproximal end of sheath 102 or on handle 202, by the nonsymmetrical shapeof the handle or by another indicator. Such indicator preferably willidentify the side of sheath 102 on which pull wire 130 is located, whichis the direction to which the distal portion of the sheath will deflect.Once the proper orientation of sheath 102 has been confirmed, the usermay operate the actuator 222 on the handle 202 of delivery device 100 tomove the distal portion of the sheath to the deflected configuration.With the proximal section 115 of sheath 102 positioned in the superiorvena cava 12 and the distal portion of the sheath deflected as shown inFIG. 19C, the distal end 120 of the sheath will point generally towardthe region in the atrial septum at which the bundle of His 30 islocated, and will be in close proximity to the septum, as shown in FIG.19D. If electrical signals are received from electrodes 310 and 312 inthis position of sheath 102, the user will know that the distal end 120of the sheath is aligned with His bundle 30.

If electrodes 310 and 312 are not receiving electrical signals, or ifthe signals are very faint, the user can maneuver the distal end 120 ofsheath 102 by small movements of actuator 222 in either a forward orreverse direction to scan the atrial wall. These small movements ofactuator 222 will deflect the distal portion of sheath 102 by smallamounts toward or away from the proximal section 115 of the sheath.Scanning in different directions can be accomplished by small rotationsof handle 202. When the signals received by electrodes 310 and 312 arethe strongest, the user can be confident that His bundle 30 has beenlocated, and the close proximity of the electrodes to one another willassure that the His bundle is directly opposite the distal end 120 ofsheath 102. With each of these movements, the distal end 120 of sheath102 remains generally perpendicular to the atrial wall. Accordingly,once this mapping procedure has located the bundle of His, pacing lead600 can be fixed in the His bundle by advancing the fixation anchor 612of the lead out from the distal end 120 of sheath 102 and rotating thelead within delivery device 100 to drive the fixation anchor into theatrial septal wall, as shown schematically in FIG. 20. Since the overallstiffness of sheath 102 is relatively high, the distal tip of the sheathwill maintain its position as fixation anchor 612 is driven into theatrial septal wall, thereby assuring that the fixation anchor will notbe diverted from its target site.

Once lead 600 has been properly fixed in the tissue of the bundle ofHis, sheath 102 can be returned to a substantially straightconfiguration by rotating actuator 222 in the direction opposite thatused for deflection. Sheath 102 may then be removed from around lead 600and from heart 10. This may be accomplished by assembling a sheathslitter 520 to the distal housing portion 210 of housing 202 so that theknife blade thereof is positioned within channel 250, as shown in FIG.21. By holding sheath slitter 520 in a substantially stationary positionwhile pulling delivery device 100 proximally, the knife blade of thesheath slitter will slice through hub 402 and along sheath 102, withoutdamaging lead 600. When it reaches electrodes 310 and 312, the knifeblade of slitter 520 will pass between the electrodes to the distal end120 of sheath 102. Once sheath 102 has been split along its entirelength, the sheath may be removed, leaving lead 600 embedded within theatrial septal wall at the bundle of His 30.

In a variant hereof, delivery device 100 may include a distal housingportion 210′, which is an alternate embodiment of distal housing portion210. A cross-sectional view of distal housing portion 210 is shown inFIG. 22A and a cross-sectional view of distal housing portion 210′ isshown in FIG. 22B. Distal housing portion 210′ is substantially similarto distal housing portion 210, with the exception of the angle at whichsheath 102 enters handle 202. In distal housing portion 210, sheath 102enters the distal housing portion through an aperture 254 and along aguide surface 256 that are oriented substantially parallel to thelongitudinal axis of handle 202. In contrast, sheath 102 enters distalhousing portion 210′ through an aperture 254′ and along a guide surface256′ that are substantially parallel to the central longitudinal axis ofhub 402. In both embodiments, sheath 102 exits housing portion 210, 210′along an axis that is parallel to the longitudinal axis of hub 402. As aresult, while distal housing portion 210 creates a bend in sheath 102for sheath slitter 520 to encounter in the initial stages of theslitting operation, distal housing portion 210′ presents the slitterwith a substantially straight sheath.

To summarize the foregoing, according to a first aspect of thedisclosure, a delivery device for delivering a pacing lead to the Hisbundle of a patient's heart includes a handle; an elongated sheathhaving a proximal end connected to the handle and a distal end remotefrom the handle, a distal portion of the sheath having a plurality offlexible sections spaced from one another along a length of the sheath;a pull wire having a distal end connected to the sheath distally of theflexible sections and extending to a proximal end; and a plurality ofmapping electrodes positioned at the distal end of the sheath; and or

-   the distal end of the sheath may have a distal tip, and the mapping    electrodes may include two electrodes that diametrically oppose one    another at a position spaced from the distal tip of the sheath;    and/or-   the two electrodes may be spaced apart by between about 1 mm and    about 3 mm in a circumferential direction of the sheath; and/or-   the distal end of the sheath may have a distal end face, and the    mapping electrodes may be exposed on the distal end face; and/or-   the distal end of the sheath may have a distal end face, and the    mapping electrodes may be spaced from the distal end face; and/or-   the flexible portions of the sheath may have a first Shore D    hardness which is less than a second Shore D hardness of remaining    portions of the sheath; and/or-   the flexible portions of the sheath may have a Shore D hardness of    between about 20 and about 40; and/or-   the flexible portions of the sheath may have a Shore D hardness of    about 35; and/or-   the remaining portions of the sheath may have a Shore D hardness of    between 60 and about 100; and/or-   the remaining portions of the sheath may have a Shore D hardness of    between 70 and about 75; and/or-   the sheath may have a substantially straight configuration in an    initial condition and a dual hinged curved configuration in a use    condition; and/or-   the handle may include a rotatable actuator, rotation of the    actuator in a first direction moving the sheath toward the use    condition and rotation of the actuator in an opposite direction    moving the sheath toward the initial condition; and/or-   the handle may include a rotatable portion and translatable portion,    the proximal end of the pull wire being connected to the    translatable portion, whereby rotation of the rotatable portion    translates the pull wire in a longitudinal direction of the sheath;    and/or-   the handle may include a proximal handle portion and a distal handle    portion, the proximal handle portion being connected to the distal    handle portion by a rail so as to define a space between the    proximal handle portion and the distal handle portion; and/or-   the rotatable actuator may be connected to the handle between the    proximal handle portion and the distal handle portion; and/or-   the handle may have a longitudinal axis and the proximal end of the    sheath may enter the handle along the longitudinal axis and may exit    the handle at an angle transverse to the longitudinal axis; and/or-   the handle may have a longitudinal axis and the proximal end of the    sheath may enter the handle at a predetermined angle transverse to    the longitudinal axis and may exit the handle at the predetermined    angle transverse to the longitudinal axis; and/or-   each of the mapping electrodes may include a pair of side edges    substantially parallel to a longitudinal axis of the sheath and a    pair of end edges substantially orthogonal to the longitudinal axis    of the sheath, and the side edges may be beveled; and/or-   each of the electrodes may be formed from a plate having a pair of    opposed side edges and a pair of opposed end edges, and the plate    may have a thickness along the side edges and along the end edges    that is less than the thickness in a center of the plate; and/or-   each of the electrodes may have a main body and a pair of end    portions projecting from opposite ends of the main body; and/or-   the end portions may project away from the main body in opposite    directions; and/or-   the main body may have an inner surface and an outer surface, and at    least one of the end portions may be bent against the inner surface    of the main body; and/or-   the pair of end portions may be bent toward one another and toward    the inner surface of the main body; and/or-   the sheath may include a first layer, a middle layer, and an outer    layer; and/or the inner layer may extend from the proximal end of    the sheath to the distal end of the sheath; and/or-   the inner layer may be formed from a lubricious material; and/or-   the lubricious material may be polytetrafluoroethylene; and/or-   the middle layer may be a braided layer including metallic braids    embedded within a polymer; and/or-   the braided layer may extend from the proximal end of the sheath to    the distal end of the sheath; and/or-   the outer layer may include a plurality of sections formed from a    polymer having a first shore D hardness and a plurality of sections    formed from a polymer having a second shore D hardness which is    greater than the first shore D hardness; and/or-   the use condition of the sheath may define a deflection plane, and    the mapping electrodes may include two electrodes that are    positioned on the sheath so that the two electrodes lie within the    deflection plane in the use condition.

According to another aspect of the disclosure, a method for delivering apacing lead to the His bundle of a patient's heart includes providing adelivery device having a sheath with an axial lumen and a distal endface; inserting the sheath into the patient' s body through the superiorvena cava until a distal end portion of the sheath is positioned in theright atrium of the patient; inserting a pacing lead into the axiallumen of the sheath; deflecting the distal end portion of the sheath sothat the distal end face of the sheath confronts the wall of the rightatrium; and moving the distal end face of the sheath relative to thewall of the right atrium until electrodes adjacent the distal end faceof the sheath receive electrical signals from the bundle of His; and/or

-   the delivery device may include a handle connected to a proximal end    of the sheath and a pull wire extending from the handle to a distal    end of the sheath, and the deflecting step may include translating    the pull wire proximally relative to the handle; and/or-   the handle may include a rotatable actuator, and the deflecting step    may include rotating the actuator in a first direction to move the    pull wire proximally relative to the handle; and/or-   the distal end portion of the sheath may include a plurality of    flexible sections spaced from one another along a length of the    sheath, and the deflecting step may include bending the sheath at    the flexible sections to place the distal end portion of the sheath    in a dual hinged curved configuration; and/or-   the method may further include the step of fixing the pacing lead to    tissue in the bundle of His.

Although the invention herein has been described with reference toparticular embodiments, it is to be understood that these embodimentsare merely illustrative of the principles and applications of thepresent invention. It is therefore to be understood that numerousmodifications may be made to the illustrative embodiments and that otherarrangements may be devised without departing from the spirit and scopeof the present invention as defined by the appended claims. For example,although the delivery device has been described herein for use inmapping the bundle of His and fixing a pacing lead therein, the deliverydevice may also be used as a component of an ablation catheter to ablatethe bundle of His. In such event, the heart could be paced usingmultiple leads in various chambers of the heart.

1. A delivery device for delivering a pacing lead to the His bundle of apatient's heart, the delivery device comprising: a handle; an elongatedsheath having a proximal end connected to the handle and a distal endremote from the handle, a distal portion of the sheath having aplurality of flexible sections spaced from one another along a length ofthe sheath; a pull wire having a distal end connected to the sheathdistally of the flexible sections and extending to a proximal end; and aplurality of mapping electrodes positioned at the distal end of thesheath.
 2. The delivery device as claimed in claim 1, wherein the distalend of the sheath has a distal tip, and the mapping electrodes includetwo electrodes that diametrically oppose one another at a positionspaced from the distal tip of the sheath.
 3. The delivery device asclaimed in claim 2, wherein the two electrodes are spaced apart bybetween about 1 mm and about 3 mm in a circumferential direction of thesheath.
 4. The delivery device as claimed in claim 1, wherein the distalend of the sheath has a distal end face, and the mapping electrodes areexposed on the distal end face.
 5. The delivery device as claimed inclaim 1, wherein the distal end of the sheath has a distal end face, andthe mapping electrodes are spaced from the distal end face.
 6. Thedelivery device as claimed in claim 1, wherein the flexible portions ofthe sheath have a first Shore D hardness which is less than a secondShore D hardness of remaining portions of the sheath.
 7. The deliverydevice as claimed in claim 6, wherein the flexible portions of thesheath have a Shore D hardness of between about 20 and about
 40. 8. Thedelivery device as claimed in claim 7, wherein the flexible portions ofthe sheath have a Shore D hardness of about
 35. 9. The delivery deviceas claimed in claim 6, wherein the remaining portions of the sheath havea Shore D hardness of between about 60 and about
 100. 10. The deliverydevice as claimed in claim 9, wherein the remaining portions of thesheath have a Shore D hardness of between about 70 and about
 75. 11. Thedelivery device as claimed in claim 1, wherein the sheath has asubstantially straight configuration in an initial condition and a dualhinged curved configuration in a use condition.
 12. The delivery deviceas claimed in claim 1, wherein the handle includes a proximal handleportion and a distal handle portion, the proximal handle portion beingconnected to the distal handle portion by a rail so as to define a spacebetween the proximal handle portion and the distal handle portion. 13.The delivery device as claimed in claim 12, further comprising arotatable actuator positioned in the space and connected to the proximalhandle portion and the distal handle portion, rotation of the actuatorin a first direction moving the sheath toward the use condition androtation of the actuator in an opposite direction moving the sheathtoward the initial condition.
 14. The delivery device as claimed inclaim 1, wherein the handle has a longitudinal axis and the proximal endof the sheath enters the handle at a predetermined angle transverse tothe longitudinal axis and exits the handle at the predetermined angletransverse to the longitudinal axis.
 15. A method for delivering apacing lead to the His bundle of a patient's heart, the methodcomprising: providing a delivery device having a sheath with an axiallumen and a distal end face; inserting the sheath into the patient'sbody through the superior vena cava until a distal end portion of thesheath is positioned in the right atrium of the patient; inserting apacing lead into the axial lumen of the sheath; deflecting the distalend portion of the sheath so that the distal end face of the sheathconfronts the wall of the right atrium; and moving the distal end faceof the sheath relative to the wall of the right atrium until electrodeson the distal end face of the sheath receive electrical signals from thebundle of His.
 16. The method as claimed in claim 15, wherein thedelivery device includes a handle connected to a proximal end of thesheath and a pull wire extending from the handle to a distal end of thesheath, and the deflecting step includes translating the pull wireproximally relative to the handle.
 17. The method as claimed in claim16, wherein the handle includes a rotatable actuator, and the deflectingstep includes rotating the actuator in a first direction to move thepull wire proximally relative to the handle.
 18. The method as claimedin claim 15, wherein the distal end portion of the sheath includes aplurality of flexible sections spaced from one another along a length ofthe sheath, and the deflecting step includes bending the sheath at theflexible sections to place the distal end portion of the sheath in adual hinged curved configuration.
 19. The method as claimed in claim 15,further comprising the step of fixing the pacing lead to tissue in thebundle of His.